Method and apparatus for performing knee arthroplasty

ABSTRACT

A set of instruments for preparing a femur and tibia for receipt of a partial knee prosthesis can include a femoral drill guide that is selectively connected to an intramedullary (IM) rod. At least one sizing spoon can communicate with the femoral drill guide. The femoral drill guide can have terminal cutting surfaces. A tibial cut guide can be selectively connected to the femoral drill guide. A dial member can be disposed on one of the femoral or tibial cut guides that when rotated moves at least one of the spoons in a superior/inferior direction.

FIELD

The present disclosure relates to a method and apparatus for preparingbone to receive an implant. In particular, the present disclosurerelates to a method and apparatus for preparing a knee joint to receivea unicondylar knee system.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

For various reasons, the human knee can fail or be damaged or worn atthe tibial and femoral juncture. When only a medial or lateral side ofthe knee is affected, the damaged portions of the tibia and/or femur canbe removed and each can be replaced with implants, conventionallyreferred to as a unicompartmental knee replacement. With respect to thetibia, the superior articulating surface of the tibia can beconventionally prepared to receive the implant by resecting a portion ofthe superior articulating bone surface. With respect to the femur, theinferior articulating surface can be conventionally prepared byresecting a portion of the inferior articulating surface. During theseresections, it may be desirable to preserve as much of the natural femuras possible. Thus, there is a need for an apparatus and/or method forresecting the superior articulating surface of the tibia and theinferior articulating surface of the femur to preserve as much of thedesired natural bone surfaces as possible.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

A set of instruments for preparing a femur and tibia for receipt of apartial knee prosthesis can include a femoral drill guide that isselectively connected to an intramedullary (IM) rod and includes atleast one terminal cutting surface. A first engagement member cancommunicate with the femoral drill guide. The first engagement membercan be configured to engage the distal femur. A second engagement membercan communicate with the femoral drill guide. The second engagementmember can be configured to engage the tibia. A tibial cut guide canselectively engage the femoral drill guide. An adjuster can be disposedon the femoral cut guide that, when rotated, moves at least one of thefirst and second engagement members in a superior/inferior direction.

According to other features, the first and second engagement members cancomprise a femoral spoon and a tibial spoon, respectively. The femoraland tibial spoons can both have arcuate profiles that occupy a commonelevation in an initial position. A cam and cam follower associated withthe femoral drill guide can be operable to communicate rotation of thedial member into translation of at least one of the first and secondengagement members. The femoral drill guide can include a first borealong a first longitudinal axis. The cam can be rotatably disposedwithin the first bore. Translation of at least one of the first andsecond engagement members can comprise translation along a secondlongitudinal axis that is transverse to the first longitudinal axis. Acam follower can ride along a groove in the cam. The cam follower can befixed to one of the first and second engagement members. One of thefirst and second engagement members can move along the secondlongitudinal axis relative to the other of the first and secondengagement members upon rotation of the cam around the firstlongitudinal axis.

According to still other features, the adjuster comprises a dial havinga locating finger that is configured to selectively and alternativelypass through a corresponding keyway provided on the femoral drill guideat multiple discrete locations. In the example provided, three keywaysare provided corresponding to three discrete offsets between the tibialand femoral spoons. The tibial cut guide can be selectively coupled tothe femoral cut guide. The tibial cut guide can be configured to extendlaterally beyond the at least one terminal cutting surface and act as acut stop for a cutting instrument that references the at least oneterminal cutting surface. In one configuration, the tibial cut guide canbe magnetically coupled to the femoral cut guide. An IM rod linkassembly can operably connect the femoral drill guide to the IM rod. TheIM rod link assembly can include an IM rod link that further includes afirst locating portion that selectively connects with the IM rod and asecond locating position that selectively connects with the femoraldrill guide. The first locating portion can comprise a first peg that isconfigured to selectively locate into a cannulation of the IM rod andthe second locating portion can comprise a second peg that is configuredto locate into a connector hole defined in the femoral drill guide.

A method for preparing a femur and tibia for receipt of a partial kneeprosthesis can include locating a femoral drill guide adjacent a femurwherein a femoral engagement member associated with the femoral drillguide is positioned adjacent the femur and a tibial engagement memberassociated with the femoral drill guide is positioned adjacent thetibia. The method can include moving an adjuster disposed on the femoraldrill guide causing at least one of the femoral and tibial engagementmembers to translate against the respective femur and tibia causing ajoint space between the femur and tibia to widen. A desired joint spacebetween the femur and tibia can be determined based on the translation.Lug holes can be prepared in the femur using bores in the femoral drillguide as a reference. The method further includes coupling a tibial cutguide to the femoral drill guide. The tibial cut guide can have an uppercutting surface. The tibia can be cut while referencing a terminalcutting surface on the femoral drill guide.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is an anterior view of an exemplary unicondylar knee prosthesisimplanted on a right knee according to one example of the presentteachings;

FIG. 2 is a medial view of the unicondylar femoral prosthesis of FIG. 1;

FIG. 3 is an anterior view of an exemplary knee joint shown in flexionprior to receiving the unicondylar knee prosthesis of FIG. 1;

FIG. 4 is an exploded perspective view of an adjustable femoral drillguide for preparing the femur and tibia for receipt of the unicondylarknee prosthesis of FIG. 1;

FIG. 5 is a rear perspective view of a dial of the adjustable femoraldrill guide illustrated in FIG. 4;

FIG. 6 is a front perspective view of the femoral drill guide body ofthe adjustable femoral drill guide of FIG. 4;

FIG. 7 is a rear perspective view of a cam of the adjustable femoraldrill guide of FIG. 4;

FIG. 8 is an exploded perspective view of an IM rod link assemblyaccording to the present teachings;

FIG. 9 is a perspective view of the IM rod link of FIG. 8 shown in anassembled position;

FIG. 10 is an anterior view of the knee illustrated in FIG. 3 and shownwith the adjustable femoral drill guide positioned relative to the kneejoint and relative to an intramedullary (IM) rod extending from thefemur via an IM rod link;

FIG. 11 is a medial view of the adjustable femoral drill guide of FIG.10 and shown with a tibial spoon and femoral spoon extending into thejoint space between the femur and tibia;

FIG. 12 is an anterior view of the knee shown in FIG. 10 and illustratedwith the dial rotated to a discrete position that corresponds with thetibial spoon being translated against the tibia to widen the joint spacebetween the femur and tibia;

FIG. 13 is an anterior view of the adjustable femoral drill guide ofFIG. 12 shown with the tibial spoon translated inferiorly against thetibia and relative to the femoral spoon that is engaged to the femur;

FIG. 14 is a medial view of the knee shown in FIG. 13 and illustratedwith a first and second drill bit drilling peg holes into the femurwhile being guided along respective bores formed through the adjustablefemoral drill guide;

FIG. 15 is a lateral view of the knee shown in FIG. 14 illustrating atibial cut block being magnetically coupled to the adjustable femoraldrill guide;

FIG. 16 is a lateral view of the knee joint of FIG. 15 and shown with asaw being guided along a terminal end surface of the femoral drill guidewhile cutting a superior/inferior cut on the tibial according to oneexample;

FIG. 17 is an anterior view of the knee joint of FIG. 16 shown with thesaw being guided along the terminal end surface of the femoral drillguide;

FIG. 18 is an anterior view of the knee of FIG. 16 and shown with thetibial cut block pinned to the tibia and the femoral drill guide removedsubsequent to cutting the superior/inferior cut on the tibia;

FIG. 19 is a superior view of the tibia shown with another cuttinginstrument performing a medial/lateral cut on the tibia; and

FIG. 20 is an anterior view of the knee shown in FIG. 18 and illustratedsubsequent to performing both of the superior/inferior andmedial/lateral cuts on the tibia for receipt of the tibial unicondylarprosthesis.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

The following description of the embodiments concerning a unicondylarfemoral prosthesis and related instruments are merely exemplary innature and are not intended to limit the disclosure or its applicationor uses. Moreover, while the present disclosure is described in detailbelow with respect to a right medial unicondylar prosthesis, it will beappreciated by those skilled in the art that the present disclosure maybe applied to various other types of knee joint prostheses, such as atotal knee joint prosthesis.

With initial reference to FIGS. 1 and 2, a unicondylar knee prosthesisimplanted using the instruments and a related method of the presentdisclosure is shown. A femur 10 is illustrated in combination with atibia 12. The femur 10 can have a femoral component 14 implantedtherein. The tibial 12 can have a tibial component 16 implanted therein.While medial implants are shown on a right knee, it should be known thatthe instruments and related method will apply to both medial and lateralcomponents, as well as left and right knees.

The tibial component 16 can include a tibial tray or platform 18 and atibial insert or bearing 20. While the exemplary tibial component 16 isshown and described as a two-piece tibial component, the tibialcomponent can have multiple pieces or alternatively can consist of asingle unitary piece. The tibial component 16 can be designed toresurface a proximal end of the tibia 12 to cooperate with theunicondylar femoral component 14. The tibial tray 18 can include agenerally D-shaped body having an attachment keel 24 extending generallyorthogonally therefrom. The D-shape extends along the transverse plane.The tibial insert 20 can be constructed from any suitable bearingmaterial, such as ultra high molecular weight polyethylene (UHMWPE). Oneexemplary tibial component is provided as part of the Oxford® PartialKnee marketed by Biomet Manufacturing Corp. of Warsaw, Ind.

The femoral component 14 can be designed to resurface the distal andposterior portions of one of the femoral condyles of the femur 10. Thefemoral component 14 can have an articulating surface 28 and a bonemating surface 30. The bone mating surface 30 can include a distalsurface 32, that transitions to a posterior surface 34. Extending fromthe bone mating surface 30 can be a peg 40. The peg 40 can aid inalignment, stability and attachment of the femoral component 14. It canbe appreciated by those skilled in the art that while the femoralcomponent 14 has been described as having a single peg 40, otherconfigurations are contemplated. For example, in another configuration,a femoral component can be constructed that includes two or more pegs.One exemplary femoral component is also provided as part of the Oxford®Partial Knee, identified above.

With brief reference now to FIG. 3, a femur 10 and tibia 12 areillustrated having respective medial and lateral ligaments 46 and 48.The femur 10 can have a medial defect 50 and the tibia 12 can have amedial defect 52. As can be appreciated, such a condition can be typicalfor a surgeon to determine that a unicondylar knee prosthesis issuitable for implantation. According to the present teachings, anintramedullary (IM) rod 54 having a cannulation 55 can be referencedfrom the femur 10. The IM rod 54 can be inserted into the IM canalaccording to conventional methods.

Turning now to FIG. 4, an adjustable femoral drill guide 56 used forpreparing the femur 10 and tibia 12 for receipt of the unicondylarprosthesis are shown. The adjustable femoral drill guide 56 cangenerally comprise a dial or adjuster 60, a femoral drill guide body 62,a spring capture 64, a spring or biasing member 66, a cam 68, a tibialengagement member or spoon 70 and a femoral engagement member or spoon72. The tibial and femoral spoons 70 and 72 can both have an arcuateprofile. A locating pin 74 can cooperate with the dial 60 and the cam68. A dowel pin 76 can cooperate with the femoral drill guide body 62and the femoral spoon 72. A cam follower 78 can cooperate with the cam68 and tibia spoon 70 as will be described in greater detail herein. Apair of magnets 80 can be fixedly secured to the femoral drill guidebody 62 by way of attachment disks 82. The attachment disks 82 can havethreaded shafts 83 that threadably mate with corresponding bores (notspecifically shown) in the femoral drill guide body 62.

With continued reference to FIG. 4 and further reference now to FIG. 5,the dial 60 will be described in greater detail. The dial 60 can be usedto translate the tibial spoon 70 relative to the femoral spoon 72 aswill be described herein. The dial 60 can generally comprise a dial body84 having a pointer portion 86 and a pair of lobes 88. A locating boss90 can extend from the body 84. The locating boss 90 can generallyinclude a cylindrical body 91 that defines an opening 92. Thecylindrical body 91 can include a locating finger 94 and a transversebore 96 that extend through diametrically opposing walls of the locatingboss 90. The bore 96 can be configured to fixedly receive the locatingpin 74 therein. The locating pin 74 engages structure on the cam 68 aswill be described. A mark or indicia 98 can be provided on an outer face100 of the body 84 (FIG. 4).

With reference now to FIGS. 4 and 6, the femoral drill guide body 62will be further described. The femoral drill guide body 62 can generallycomprise a body 104 having a tower 106 that generally extendstransversely relative to a base 107. As will become appreciated from thefollowing discussion, the base 107 can have a terminal medial cuttingsurface 108 a that can be configured to guide a cutting instrument suchas a sagittal saw 254 for preparation of a vertical (i.e.,superior/inferior) cut 260 (FIG. 19) in the tibia 12. The base 107 canalso have a terminal medial cutting surface 108 b (FIG. 4) that can bereferenced when performing surgery on a left knee. The femoral drillguide body 62 can have a cylinder 109 that defines a bore 110. The bore110 can be positioned generally at a transition between the tower 106and the base 107. The bore 110 can generally define a throughbore thatextends from a front or first opening 112 to a rear or second opening114. The body 104 can include a first keyway 120, second keyway 122 andthird keyway 124 at the front opening 112. The respective first, secondand third keyways 120, 122 and 124 can include a shape that is generallycomplementary to the locating finger 94 of the dial 60. A pair ofaligned side bores 130 can be formed at diametrically opposed locationsin the body 104 generally transverse to a long axis 132 of the bore 110.The femoral drill guide body 62 can have a lower surface 133 that ismagnetic from the magnets 80.

The cylinder 109 of the femoral drill guide body 62 can provide a cutout134 thereon. The tower 106 can define a pair of connector holes 136therein. The connector holes 136 define axes 138 that angle toward thenearest sidewall of the tower 106. The respective axes 138 can eachangle toward the nearest sidewall an angle of about 7°. In this regard,the axes 138 can be about 14° relative to each other. As will bedescribed, an IM rod link assembly 200 can engage one of the connectorholes 136 and the cannulation 55 in the IM rod 54. The axes 138 canextend on an angle to match the angle of a typical IM canal, i.e., 7degrees. Other angles are contemplated. Two holes 136 are provided sothat the femoral drill guide body can be used for both right and leftknees. A first longitudinal throughbore 140 and a second longitudinalthroughbore 142 can be defined through the tower 106 of the body 104.The throughbores 140 and 142 can be formed along respective parallellongitudinal axes 144 and 146. According to one example, the axes 144and 146 can be parallel relative to each other and parallel relative tothe axis 132 of the bore 110. As will become appreciated from thefollowing discussion, the throughbores 140 and 142 can be used to guidea cutting instrument such as a drill bit for formation of femoral pegholes 148, 149 (FIG. 14) in the femur 10 for receipt of the pegs 40 and42, respectively (FIG. 2).

Turning now to FIG. 7, the cam 68 will be described in greater detail.The cam 68 can generally comprise an elongated cylindrical rod 150 thatextends from a center point of a disk 152. As will be described, the cam68 can convert rotational motion of the dial 60 into linear translationof the tibial spoon 70. The rod 150 can generally be formed along alongitudinal axis 154. A slot 156 can be formed through the rod 150 forreceipt of the locating pin 74 (FIG. 4). The disk 152 can include agroove 160 formed thereon. The groove 160 can generally extend in amanner having an increasing radius from a first end 162 to a second end164. In general, the first end 162 can initiate on the disk 152 at afirst distance 166 from the longitudinal axis 154. The second end 164can terminate at a second distance 168 from the longitudinal axis 154.In this regard, the second distance 168 can be greater than the firstdistance 166. As will become appreciated from the following discussion,the cam follower 78 can be configured to ride along the groove 160between the first end 162 and the second end 164 during rotation of thecam 68 around the longitudinal axis 154. Movement of the cam follower 78along the groove 160 can cause the cam follower 78 to translate awayfrom or toward the longitudinal axis 154, which can cause the tibialspoon 70 to translate away from or toward the femoral spoon 72.

Returning now with specific reference to FIG. 4, the tibial spoon 70 andfemoral spoon 72 will be described in further detail. The tibial spoon70 can generally include a heel 170 and a pair of feet 172. The feet 172can be generally connected to the heel 170 by way of an intermediatebody portion 174. An aperture 176 can be formed in the heel 170 forreceipt of a portion of the cam follower 78. According to one example,the feet 172 can be curved in a profile that generally matches theposterior femur (FIG. 9). The femoral spoon 72 can generally comprise acylindrical body portion 180 having a foot 182 extending therefrom thatcan engage the distal femur 10. In one advantage with the instantconfiguration, the foot 182 can have the same curved profile as the feet172. Because the foot 182 is configured to locate intermediate the feet172 prior to adjusting the dial 60 (FIG. 9), the foot 182 and feet 172can occupy a common space in the transverse plane. In this regard, thefeet 172 and foot 182 can be located into the joint space with minimaldisturbance of the host bone and/or tissue. A throughbore 184 can beformed through the cylindrical body portion 180 for receipt of the dowelpin 76. More specifically, the dowel pin 76 can fixedly locate throughthe side bores 130 on the femoral drill guide body 62 and through thethroughbore 184 to fixedly secure the cylindrical body portion 180 ofthe femoral spoon 72 into the bore 110. The cylindrical body portion 180can further include a channel 188 in which the heel 170 can slidablynest. The cutout 134 (FIG. 6) on the cylinder 109 can provide a geometrythat accommodates passage of the heel 170 of the tibial spoon 70.

With additional reference now to FIGS. 8-12, the adjustable femoraldrill guide 56 will be described in an assembled position and relativeto the femur 10 and tibia 12. According to one example, an IM rod linkassembly 200 can fixedly connect the IM rod 54 to the femoral drillguide body 62. The IM rod link assembly 200 can generally comprise afirst locating portion 202, a second locating portion 204, a handleportion 206 and a locking ring 208. The first locating portion 202 has ashaft 210, a connecting plate 212 and a locating peg 214. The secondlocating portion 204 has a body 216 having a cannulation 217, aconnection plate 218 and a locating peg 219. The shaft 210 can berotatably received by the cannulation 217. The locking ring 208 canaxially fix the second locating portion 204 to the first locatingportion 202. The exploded view of FIG. 8 is provided for illustrativepurposes. The IM rod link assembly is provided to the user as anassembled tool that will not be disassembled by the user. In thisregard, the handle portion 206 can be securely fixed, such as bywelding, to the second locating portion 204 at the body 216. As willbecome appreciated herein, the locating peg 214 can selectively locateinto the cannulation 55 and the locating peg 219 can selectively locateinto one of the connector holes 136 to position the femoral drill guiderelative to the IM rod 54.

In the exemplary initial position illustrated in FIG. 11, the foot 172of the tibial spoon 70 and the foot 182 of the femoral spoon 72 aregenerally aligned at the same elevation. In this regard, the foot 182 ofthe femoral spoon 72 can be positioned between the feet 172 of thetibial spoon 70. Again, the femoral spoon 72 is fixed relative to thefemoral drill guide body 62 by way of the dowel pin 76. The tibial spoon70 can be selectively translated downwardly as viewed in FIG. 11 or moreparticularly in a direction inferiorly toward the tibia 12 forincreasing a gap or joint space between the femur 10 and the tibia 12.In general, rotation of the dial 60 can cause the cam follower 78 toride around the groove 160 in the disk 152 of the cam 68 causing the camfollower 78 (connected to the aperture 176 in the heel 170 of the tibialspoon 70) to urge the tibial spoon 70 into the tibia 12 to increase thejoint space between the femur 10 and tibia 12.

An exemplary method of increasing the joint space by using theadjustable femoral drill guide 56 according to one example of thepresent teachings will now be described with reference to FIGS. 10-13.The femoral drill guide body 62 can have a first indicia 220, a secondindicia 222 and a third indicia 224 formed thereon for alignment withthe mark 98 on the dial 60. According to the exemplary configuration,the corresponding indicia 220, 222 and 224 can represent one millimeterdifference in spacing between the feet 172 of the tibial spoon 70 andthe foot 182 of the femoral spoon 72 (e.g., one millimeter difference injoint space between the femur 10 and tibia 12).

At the outset, a user can depress the dial 60 in a direction along thelongitudinal axis 154 toward the femoral drill guide body 62 against thebias of the spring 66. In this regard, the locating finger 94 can beadvanced through the first keyway 120 while the locating pin 74 cantravel along the slot 156 of the cam 68. This movement disengages thelocating finger 94 from the keyway 120 to allow it to rotate freely.Next, the user can rotate the dial 60 in a direction counter-clockwiseas viewed from FIG. 8 causing the cam 68 to rotate around thelongitudinal axis 154 (FIG. 7). Rotation of the cam 68 around thelongitudinal axis 154 can cause the cam follower 78 to ride around thegroove 160 from a location generally at the first end 162 to a directiontoward the second end 164 (or in a position generally radiallyinwardly). As a result, the cam follower 78 can be caused to urge thetibial spoon 70 downwardly (inferiorly into the tibia 12) as viewed inFIG. 13. Concurrently, the heel 170 can slidably translate through thechannel 188 of the femoral spoon 72 and through the cutout 134 of thefemoral drill guide body 62. The user can then release the dial 60 toallow the spring 66 to bias the dial 60 outwardly to locate the locatingfinger 94 into one of the other keyways 122 or 124.

As illustrated in FIG. 12, the dial 60 has been released, such that thespring 66 urges the locating finger 94 into the third keyway 124corresponding to the third indicia 224. In this position, the camfollower 78 can ride around the groove 160 to a position at the secondend 164 (FIG. 7) causing the tibial spoon 70 to translate furtherdownwardly (as viewed in FIG. 13) into the tibia causing the joint spaceto widen. At this time, the surgeon can determine a proper joint tensionwith the knee in flexion and with the respective tibial and femoralspoons 70 and 72 located against the tibia and femur as illustrated inFIG. 13. The desired offset between the respective tibial and femoralspoons 70 and 72 is now determined. While the exemplary configurationcomprises an apparatus and method for moving the tibia 12 relative tothe femur 10, the femur 10 can be moved additionally or alternativelyrelative to the tibia 12.

Once the surgeon has determined the desired offset between therespective tibial and femoral spoons 70 and 72, the femoral peg holes148, 149 can be prepared into the femur 10. The lug hole 149 can receivethe peg 40. The lug hole 148 can be provided for receiving a peg ofother femoral implants that may incorporate two pegs. Additionally, oralternatively, the lug hole 148 can be used with the lug hole 149 tofacilitate rotational stability of the femoral drill guide body 62. Withreference to FIG. 14, a first drill bit 230 can be guided through thethroughbore 140 of the tower 106 on the femoral drill guide body 62 forpreparation of the first hole 148. Similarly, a second drill bit 232 canbe guided through the second throughbore 142 in the tower 106 of thefemoral drill guide body 62 for preparation of the second hole 149 inthe femur 10. It will be appreciated that during the drilling of theholes 148 and 149 for the femoral pegs 40 and 42, respectively, thelocating peg 214 of the IM rod link assembly 200 can be located into thecannulation 55 of the IM rod 54 while the locating peg 219 can belocated into one of the connecting holes 136 of the femoral drill guidebody 62. Because the shaft 210 of the first locating portion 202 isrotatably received within the cannulation 217 of the second locatingportion 204, the relative position between the first and second locatingpegs 214 and 219 is variable to accommodate various femoral and tibialspacing of a range of patients. However, in some instances, the IM rodlink assembly 200 may not be used. According to one example, the drillbits 230 and 232 can be retained in the holes 148 and 149 prepared inthe femur 10 while the IM rod link 202 and IM rod 54 are removed.

Turning now to FIGS. 15-17, a surgeon can couple a tibial cut guide 250to the base 107 of the femoral drill guide body 62, while the drill bits230 and 232 are retained in the bone holes 148 and 149. According to oneexample, the tibial cut guide 250 can be magnetically coupled to thebase 107 using the magnets 80. Specifically, an upper surface 252 canmagnetically engage the lower surface 133 of the femoral drill guidebody 62. Once the tibial cut guide 250 is coupled to the femoral drillguide body 62, the tibial cut guide 250 can be fixed relative to thetibia 12, such as by way of pins 264. A cutting instrument 254 can thenbe used to prepare a vertical (i.e., superior/inferior) cut 260 in thetibia 12. The cutting instrument 254 can reference (engage) the terminalmedial cutting surface 108 a while making the vertical cut 260 (see alsoFIG. 18). Because the tibial cut guide 250 extends more laterally thanthe terminal medial cutting surface 108 a, the upper surface 252 can actas a stop surface for the vertical cut 260. The upper surface 252 cantherefore set a depth of cut for the vertical cut 260. Once the verticalcut 260 has been prepared in the tibia 12, the drills 230 and 232 andthe adjustable femoral drill guide body 62 can be removed. (FIG. 18). Acutting instrument 270 can then be used to prepare the horizontal(medial/lateral) cut 266 on the tibia 12 (FIG. 20) while referencing(engaging) the upper surface 252. The tibial cut guide 250 can then beremoved and the tibia 12 is ready for receipt of the tibial component16. The femur 10 can then be cut for receipt of the femoral component14.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A set of instruments for preparing a femur andtibia for receipt of a partial knee prosthesis comprising: a femoraldrill guide that is selectively connected to an intramedullary (IM) rod,the femoral drill guide including a first cutting surface configured todirect a first cutting instrument to the tibia to make a first cut inthe tibia that extends in a superior/inferior direction when the femoraldrill guide is connected to the IM rod; a first engagement member thatcommunicates with the femoral drill guide and is configured to engagethe femur; a second engagement member that communicates with the femoraldrill guide and is configured to engage the tibia; a tibial cut guideconfigured to be removably coupled to the femoral drill guide, thetibial cut guide including a second cutting surface configured to directa second cutting instrument to the tibia to make a second cut in thetibia that extends in a medial/lateral direction; an adjuster disposedon the femoral drill guide that, when actuated, moves at least one ofthe first and second engagement members in a superior/inferiordirection; wherein the first and second engagement members are bothbetween the tibial cut guide and an intramedullary rod engagementportion of the femoral drill guide.
 2. The set of instruments of claim 1wherein the first and second engagement members comprise a femoral spoonand a tibial spoon, respectively, the femoral and tibial spoons bothhaving arcuate profiles that occupy a common elevation in an initialposition; and wherein the first cutting surface is adjacent to thesecond cutting surface when the tibial cut guide is coupled to thefemoral drill guide.
 3. The set of instruments of claim 2, furthercomprising a cam associated with the femoral drill guide that isoperable to communicate rotation of the adjuster into translation of atleast one of the first and second engagement members.
 4. The set ofinstruments of claim 3 wherein the femoral drill guide defines a firstbore along a first longitudinal axis and wherein the cam is rotatablydisposed within the first bore.
 5. The set of instruments of claim 4wherein translation of at least one of the first and second engagementmembers comprises translation along a second longitudinal axis that istransverse to the first longitudinal axis.
 6. The set of instruments ofclaim 5, further comprising a cam follower that rides along a groove inthe cam upon rotation of the cam, the cam follower fixed to one of thefirst and second engagement members causing one of the first and secondengagement members to move along the second longitudinal axis relativeto the other of the first and second engagement members.
 7. The set ofinstruments of claim 3 wherein the adjuster comprises a dial having alocating finger that is configured to selectively and alternatively passthrough a corresponding keyway provided on the femoral drill guide atthree discrete locations corresponding to three discrete offsets betweenthe tibial and femoral spoons.
 8. The set of instruments of claim 3wherein the tibial cut guide is configured to extend laterally beyondthe first cutting surface of the femoral drill guide when coupledthereto, and is configured to act as a cut stop for the first cuttinginstrument guided by the first cutting surface.
 9. The set of instrumentof claim 8 wherein the tibial cut guide is magnetically coupled to thefemoral drill guide.
 10. The set of instruments of claim 3, furthercomprising an IM rod link assembly that operably aligns the femoraldrill guide to the IM rod.
 11. The set of instruments of claim 10wherein the IM rod link assembly comprises a first locating portion thatselectively connects with the IM rod and a second locating portion thatselectively connects with the femoral drill guide.
 12. The set ofinstruments of claim 11 wherein the first locating portion comprises afirst peg that is configured to selectively locate into a cannulation ofthe IM rod and the second locating portion comprises a second peg thatis configured to locate into a connector hole defined in the femoraldrill guide.
 13. A set of instruments for preparing both a femur and atibia for receipt of a partial knee prosthesis comprising: a femoraldrill guide including: an intramedullary rod engagement portionconfigured to couple the femoral drill guide to an intramedullary rodseated within the femur; and a first tibia cutting surface configured todirect a first cutting instrument to the tibia to make a first tibia cuttherein; a tibial cut guide configured to be removably coupled to thefemoral drill guide and including a second tibia cutting surfaceconfigured to direct a second cutting instrument to the tibia to make asecond tibia cut therein; a first engagement member in communicationwith the femoral drill guide and configured to engage the femur; asecond engagement member in communication with the femoral drill guideand configured to engage the tibia; and an engagement member adjusterdisposed on the femoral drill guide that, when actuated, moves at leastone of the first and second engagement members together or apart;wherein the first and second engagement members are between, andlaterally offset from, the intramedullary rod engagement portion and thetibial cut guide when the tibial cut guide is coupled to the femoraldrill guide.
 14. The set of instruments of claim 13, wherein the firsttibia cut is a superior/inferior tibia cut and the second tibia cut is amedial/lateral tibia cut.
 15. The set of instruments of claim 13,wherein the first and second tibia cutting surfaces are adjacent to, andperpendicular to, each other when the tibial cut guide is coupled to thefemoral drill guide.
 16. The set of instruments of claim 13, wherein thefemoral drill guide further includes a cam coupled to the firstengagement member or the second engagement member such that rotation ofthe cam in a first direction moves the first and second engagementmembers apart, and rotation of the cam in a second direction moves thefirst and second engagement members together.
 17. A set of instrumentsfor preparing both a femur and a tibia for receipt of a partial kneeprosthesis comprising: a femoral drill guide body including anintramedullary rod engagement portion configured to couple with anintramedullary rod seated within the femur; a first tibial cut guidedefined by a first tibial cutting surface of the femoral drill guidebody, the first tibial cut guide configured to direct a first cuttinginstrument to the tibia to make a first tibia cut in the tibia thatextends in a superior/inferior direction when the femoral drill guidebody is connected to the intramedullary rod; a second tibial cut guideconfigured to be removably coupled to the femoral drill guide bodyproximate to the first tibial cut guide, the second tibial cut guideincluding a second tibial cutting surface configured to direct a secondcutting instrument to the tibia to make a second tibia cut therein thatextends in a medial/lateral direction; a femoral engagement membercoupled to the femoral drill guide body; a tibial engagement membercoupled to the femoral drill guide body; and an adjustment membercoupled to the femoral drill guide body, actuation of the adjustmentmember moves the femoral engagement member and the tibial engagementmember together or apart; wherein the femoral engagement member and thetibial engagement member are both between, and laterally offset from,the intramedullary rod engagement portion and the second tibial cutguide when the second tibial cut guide is coupled to the femoral drillguide.
 18. The set of instruments of claim 17, wherein the femoral drillguide body houses a cam coupled to the first engagement member or thesecond engagement member such that rotation of the cam in a firstdirection moves the first and second engagement members apart, androtation of the cam in a second direction moves the first and the secondengagement members together.